Low-E matchable coated articles having doped seed layer under silver, and corresponding methods

ABSTRACT

A low-E coating has good color stability (a low ΔE* value) upon heat treatment (HT). The provision of an as-deposited crystalline or substantially crystalline layer of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under an infrared (IR) reflecting layer of or including silver in a low-E coating has effect of significantly improving the coating&#39;s thermal stability (i.e., lowering the ΔE* value). One or more such crystalline, or substantially crystalline, layers may be provided under one or more corresponding IR reflecting layers comprising silver.

This invention relates to low-E coated articles that have approximately the same color characteristics as viewed by the naked eye both before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such articles may in certain example embodiments combine: (1) high visible transmission characteristics when desired, (2) good durability before and/or after heat treatment, and/or (3) a low ΔE* value which is indicative of color stability upon heat treatment (HT). Such coated articles may be used monolithically for windows, in insulating glass (IG) window units, laminated window units, vehicle windshields, and/or other vehicle or architectural or residential window applications.

BACKGROUND OF THE INVENTION

Low-emissivity (low-E) coating systems are known in the art. For example, commonly owned U.S. Pat. No. 5,376,455 discloses: glass/Si₃N₄/NiCr/Ag/NiCr/Si₃N₄. Unfortunately, the low-E coating system of the '455 patent is not sufficiently color matchable after heat treatment (HT) with its non-heat treated counterpart.

The need for substantial matchability (before heat treatment vs. after heat treatment) is known. Glass substrates are often produced in large quantities and cut to size in order to fulfill the needs of a particular situation such as a new multi-window and door office building, vehicle window needs, etc. It is often desirable in such applications that some of the windows and/or doors be heat treated (i.e., tempered, heat strengthened or heat-bent) while others need not be. Office buildings often employ IG units and/or laminates for safety and/or thermal control. It is desirable that the units and/or laminates which are heat treated (HT) substantially match their non-heat treated counterparts (e.g., with regard to color, reflectance, and/or the like, at least on the side to be viewed from outside the building) for architectural and/or aesthetic purposes.

Commonly owned U.S. Pat. No. 5,688,585 discloses a solar control coated article including: glass/Si₃N₄/NiCr/Si₃N₄. One object of the '585 patent is to provide a sputter coated layer system that after heat treatment (HT) is matchable colorwise with its non-heat treated counterpart. While the coating systems of the '585 patent are excellent for their intended purposes, they suffer from certain disadvantages. In particular, they tend to have rather high emissivity and/or sheet resistance values (e.g., because no silver (Ag) layer is disclosed in the '585 patent).

It has in the prior art been possible to achieve matchability in systems other than those of the aforesaid '585 patent, between two different layer systems, one of which is heat treated and the other is not. The necessity of developing and using two different layer systems to achieve matchability creates additional manufacturing expense and inventory needs which are undesirable.

U.S. Pat. Nos. 6,014,872 and 5,800,933 (see Example B) disclose a heat treatable low-E layer system including: glass/TiO₂/Si₃N₄/NiCr/Ag/NiCr/Si₃N₄. Unfortunately, when heat treated this low-E layer system is not approximately matchable colorwise with its non-heat treated counterpart (as viewed from the glass side). This is because this low-E layer system has a ΔE* (glass side) value greater than 4.1 (i.e., for Example B, Δa*_(G) is 1.49, Δb*_(G) is 3.81, and ΔL* (glass side) is not measured; using Equation (1) below then ΔE* on the glass side must necessarily be greater than 4.1 and is probably much higher than that).

U.S. Pat. No. 5,563,734 discloses a low-E coating system including: substrate/TiO₂/NiCrN_(x)/Ag/NiCrN_(x)/Si₃N₄. Unfortunately, it has been found that when high Nitrogen (N) flow rates are used when forming the NiCrN_(x) layers (see the high N flow rate of 143 sccm in Table 1 of the '734 patent; translating into about 22 sccm/kW), the resulting coated articles are not color stable with heat treatment (i.e., they tend to have high ΔE* (glass side) values greater than 6.0). In other words, if subjected to HT, the '734 patent low-E layer system would not be approximately matchable colorwise with its non-heat treated counterpart (as viewed from the glass side).

Moreover, it is sometimes desirable for a coated article to have high visible transmission characteristics and/or good durability (mechanical and/or chemical). Unfortunately, certain known steps that are taken to improve visible transmission characteristics and/or pre-HT durability tend to degrade post-HT durability and thermal stability. Thus, it is often difficult to obtain a combination of high visible transmission, thermal stability of color, and good durability.

In view of the above, it will be apparent to those skilled in the art that there exists a need for a low-E coating or layer system that after HT substantially matches in color and/or reflection (as viewed by a naked human eye) its non-heat treated counterpart. In other words, there exists a need in the art for a low-E matchable coating or layering system. There also exists a need in the art for a heat treatable system that can combine one or more of: (1) high visible transmission characteristics, (2) good durability before and/or after heat treatment, and/or (3) a low ΔE* value which is indicative of color stability upon heat treatment.

It is a purpose of this invention to fulfill one or more of the above-listed needs, and/or other needs which will become more apparent to the skilled artisan once given the following disclosure.

SUMMARY

An example object of this invention is to provide a low-E coating or layer system that has good color stability (a low ΔE* value) upon heat treatment (HT). Another example object of this invention is to provide a low-E matchable coating or layering system.

Example embodiments of this invention relate to low-E coated articles that have approximately the same color characteristics as viewed by the naked eye both before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such articles may in certain example embodiments combine: (1) high visible transmission characteristics when desired, (2) good durability before and/or after heat treatment, and/or (3) a low ΔE* value which is indicative of color stability upon heat treatment (HT).

Surprisingly, and unexpectedly, it has been found that the provision of an as-deposited crystalline or substantially crystalline (e.g., at least 50% crystalline, more preferably at least 60% crystalline) layer of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under an infrared (IR) reflecting layer of or including silver in a low-E coating has effect of significantly improving the coating's thermal stability (i.e., lowering the ΔE* value). One or more such crystalline, or substantially crystalline (e.g., at least 50% crystalline, more preferably at least 60% crystalline), layers may be provided under one or more corresponding IR reflecting layers comprising silver, in various embodiments of this invention. Thus, the crystalline or substantially crystalline layer of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under an infrared (IR) reflecting layer of or including silver may be used in single silver low-E coatings, double-silver low-E coatings, or triple silver low-E coatings in various embodiments of this invention. In certain example embodiments, the crystalline or substantially crystalline layer of or including zinc oxide is doped with from about 1-30% Sn, more preferably from about 1-20% Sn, more preferably from about 5-15% Sn, with an example being about 10% Sn (in terms of wt. %). The zinc oxide, doped with Sn, is in a crystallized or substantially crystallized phase (as opposed to amorphous or nanocrystalline) as deposited, such as via sputter deposition techniques from at least one sputtering target(s) of or including Zn and Sn. The crystallized phase of the doped zinc oxide based layer as deposited, combined with the layer(s) between the silver and the glass, allows the coated article to realize improved thermal stability upon optional HT (lower the ΔE* value). It is believed that the crystallized phase of the doped zinc oxide based layer as deposited (e.g., at least 50% crystalline, more preferably at least 60% crystalline), combined with the layer(s) between the silver and the glass, allows the silver deposited thereover to have improved crystal structure with texture but with some randomly oriented grains so that its refractive index (n) changes less upon optional HT, thereby allowing for improved thermal stability to be realized.

In certain example embodiments, it has also been surprisingly and unexpectedly found that the provision of a dielectric layer of or including silicon oxide, zirconium oxide, silicon zirconium oxide and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, and/or SiZrO_(x)N_(y)) provides for further improved thermal stability of the coated article, and thus even lower the ΔE* values upon heat treatment (HT) such as thermal tempering. The dielectric layer of or including silicon oxide, zirconium oxide, silicon zirconium oxide and/or silicon zirconium oxynitride may be provided directly under and contacting the lowermost doped zinc oxide based layer in certain example embodiments of this invention. It has also been surprisingly and unexpectedly found that the provision of no silicon nitride based layer directly under and contacting the lowermost doped zinc oxide based layer between the glass substrate and the lowermost silver based layer, in combination with the crystallized phase of the doped zinc oxide based layer as deposited, allows for improved thermal stability upon heat treatment (lower ΔE* values) to be realized. In certain example embodiments, it has surprisingly and unexpectedly been found that providing an absorber layer (e.g., NiCr, NiCrN_(x), NbZr, and/or NbZrN_(x)) between the glass substrate and the dielectric layer of or including silicon oxide, zirconium oxide, silicon zirconium oxide and/or silicon zirconium oxynitride (e.g., SiZrO_(x) and/or SiZrO_(x)N_(y)) advantageously reduces glass side visible reflection (R_(g)Y) of the coated article in a desirable manner and allows the visible transmission to be tuned in a desirable manner.

In certain example embodiments, measured monolithically, the coated article is configured to realize one or more of: (i) a transmissive ΔE* value (where transmissive optics are measured) of no greater than 3.0 (more preferably no greater than 2.5, and most preferably no greater than 2.3) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value (where glass side reflective optics are measured) of no greater than 3.0 (more preferably no greater than 2.0, and most preferably no greater than 1.0) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C., and/or (iii) a film side reflective ΔE* value (where film side reflective optics are measured) of no greater than 3.5 (more preferably no greater than 3.0, and most preferably no greater than 2.0) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C. In certain example embodiments, measured monolithically, the coated article is configured to have a visible transmission (T_(vis) or Y), before or after any optional HT, of at least about 50%, more preferably of at least about 60%, and most preferably of at least about 68% or 70%. In certain example embodiments, measured monolithically, the coated article is configured to have a glass side visible reflection (R_(g)Y), measured monolithically, before or after any optional HT, of no greater than 16%, more preferably no greater than 15%, and most preferably no greater than 14%.

In an example embodiment of this invention, there is provided a coated article including a coating on a glass substrate, wherein the coating comprises: a first crystalline or substantially crystalline layer (e.g., at least 50% crystalline, more preferably at least 60% crystalline) comprising zinc oxide doped with from about 1-30% Sn (wt. %), provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn; wherein no silicon nitride based layer is located directly under and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn between the glass substrate and the first IR reflecting layer comprising silver; and wherein the coated article is configured to have, measured monolithically, one, two, or all three of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C. The first crystalline or substantially crystalline layer comprising zinc oxide may be doped with from about 1-20% Sn (wt. %) (or other suitable dopant), more preferably with from about 5-15% Sn (wt. %), and most preferably with about 10% Sn (wt. %).

In an example embodiment of this invention, there is provided coated article including a coating on a glass substrate, wherein the coating comprises: a crystalline or substantially crystalline layer comprising zinc oxide doped with at least one metal (e.g., Sn) provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the layer comprising zinc oxide doped with at least one metal; at least one dielectric layer on the glass substrate over at least the first IR reflecting layer comprising silver and the layer comprising zinc oxide doped with at least one metal; wherein no silicon nitride based layer is located directly under and contacting the layer comprising zinc oxide doped with at least one metal; a second IR reflecting layer comprising silver located over at least the first IR reflecting layer; a dielectric layer comprising an oxide of silicon and zirconium located on the glass substrate between at least the glass substrate and the layer comprising zinc oxide doped with at least one metal; and wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.

Such coated articles may be used monolithically for windows, in insulating glass (IG) window units (e.g., on surface #2 or surface #3 in IG window unit applications), laminated window units, vehicle windshields, and/or other vehicle or architectural or residential window applications.

This invention will now be described with respect to certain embodiments thereof as illustrated in the following drawings, wherein:

IN THE DRAWINGS

FIGS. 1(a), 1(b), 1(c), and 1(d) are cross sectional views of coated articles according to example embodiments of this invention.

FIG. 2 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 1 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 3 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 2 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 4 is a chart illustrating optical characteristics of Example 1: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 5 is a chart illustrating optical characteristics of Example 2: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 6 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 3 on a 3.1 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 7 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 4 on a 3.1 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 8 is a chart illustrating optical characteristics of Examples 3-4: as coated (annealed) before heat treatment in the left-most data column, after 8 minutes of heat treatment at 650 degrees C. (HT), after 12 minutes of HT at 650 degrees C. (HTX), and after 20 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 9 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 5 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 10 is a chart illustrating optical characteristics of Example 5: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 11 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 6 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 12 is a chart illustrating optical characteristics of Example 6: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 13 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 7 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 14 is a chart illustrating optical characteristics of Example 7: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 15 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 8 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 16 is a wavelength (nm) vs. refractive index (n) graph illustrating the change in refractive index of the silver layer of Example 8 from the as coated (AC) state to the heat treated (HT) state.

FIG. 17 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 9 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(a).

FIG. 18 is a chart illustrating optical characteristics of Example 9: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), and after 16 minutes of HT at 650 degrees C. (HTX) in the far right data column.

FIG. 19 is a cross sectional view of a first Comparative Example coated article.

FIG. 20 is a cross sectional view of a coated article according to an embodiment of this invention, illustrating coatings of Examples 1-10.

FIG. 21 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 10 on a 3.1 mm thick glass substrate, where the low-E coating is illustrated in general by FIGS. 1(a) and 10.

FIG. 22 is an XRD Lin (Cps) vs. 2-Theta-Scale graph illustrating, for Example 10, the relative small 66% change in peak height of Ag (111) due to HT.

FIG. 23 is an XRD Lin (Cps) vs. 2-Theta-Scale graph illustrating, for the first Comparative Example (CE), the relative large 166% change in peak height of Ag (111) due to HT.

FIG. 24 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 11 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(b).

FIG. 25 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 12 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(b).

FIG. 26 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 13 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(b).

FIG. 27 is a chart illustrating optical characteristics of Examples 11-13: as coated (annealed) before heat treatment in the left-most data column of each, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column of each.

FIG. 28 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Example 14 on a 6 mm thick glass substrate, where the low-E coating is illustrated in general by FIG. 1(b).

FIG. 29 is a chart illustrating optical characteristics of Example 14: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

FIG. 30 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coatings of Examples 15 and 16 on 6 mm thick glass substrates, where the low-E coatings of these examples are illustrated in general by FIG. 1(b) with a bottommost dielectric layer of ZrO₂.

FIG. 31 is a chart illustrating optical characteristics of Examples 15 and 16: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), and after 16 minutes of HT at 650 degrees C. (HTX) in the far right data column.

FIG. 32 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coatings of Examples 17 and 18 on 6 mm thick glass substrates, where the low-E coatings of these examples are illustrated in general by FIG. 1(b) with a bottommost dielectric layer of SiO₂ doped with about 8% Al (wt. %) FIG. 33 is a chart illustrating optical characteristics of Examples 17 and 18: as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), and after 16 minutes of HT at 650 degrees C. (HTX) in the far right data column.

FIG. 34 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Comparative Example 2 (CE 2) on a 6 mm thick glass substrate.

FIG. 35 is a chart illustrating optical characteristics of Comparative Example 2 (CE 2): as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column.

DETAILED DESCRIPTION OF CERTAIN EXEMPLARY EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts/layers/materials throughout the several views.

Certain embodiments of this invention provide a coating or layer system that may be used in coated articles that may be used monolithically for windows, in insulating glass (IG) window units (e.g., on surface #2 or surface #3 in IG window unit applications), laminated window units, vehicle windshields, and/or other vehicle or architectural or residential window applications. Certain embodiments of this invention provide a layer system that combines one or more of high visible transmission, good durability (mechanical and/or chemical) before and/or after HT, and good color stability upon heat treatment. It will be shown herein how certain layers stacks surprisingly enable this unique combination.

With regard to color stability, certain embodiments of this invention have excellent color stability (i.e., a low value of ΔE*; where Δ is indicative of change in view of heat treatment) with heat treatment (e.g., thermal tempering or heat bending) monolithically and/or in the context of dual pane environments such as IG units or windshields. Such heat treatments (HTs) often necessitate heating the coated substrate to temperatures of at least about 1100° F. (593° C.) and up to 1450° F. (788° C.) [more preferably from about 1100 to 1200 degrees F., and most preferably from 1150-1200 degrees F.] for a sufficient period of time to insure the end result (e.g., tempering, bending, and/or heat strengthening). Certain embodiments of this invention combine one or more of (i) color stability with heat treatment, and (ii) the use of a silver inclusive layer for selective IR reflection.

Example embodiments of this invention relate to low-E coated articles that have approximately the same color characteristics as viewed by the naked eye both before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such articles may in certain example embodiments combine one or more of: (1) high visible transmission characteristics when desired, (2) good durability before and/or after heat treatment, and/or (3) a low ΔE* value which is indicative of color stability upon heat treatment (HT).

Surprisingly, and unexpectedly, it has been found that the provision of an as-deposited crystalline or substantially crystalline layer 3 (and/or 13) (e.g., at least 50% crystalline, more preferably at least 60% crystalline) of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under and directly contacting an infrared (IR) reflecting layer of or including silver 7 (and/or 19) in a low-E coating 30 has the effect of significantly improving the coating's thermal stability (i.e., lowering the ΔE* value). “Substantially crystalline” as used herein means at least 50% crystalline, more preferably at least 60% crystalline, and most preferably at least 70% crystalline. One or more such crystalline, or substantially crystalline, layers 3, 13 may be provided under one or more corresponding IR reflecting layers comprising silver 7, 19, in various example embodiments of this invention. Thus, the crystalline or substantially crystalline layer 3 and/or 13 of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under an infrared (IR) reflecting layer 7 and/or 19 of or including silver may be used in single silver low-E coatings, double-silver low-E coatings (e.g., such as shown in FIG. 1 or FIG. 20), or triple silver low-E coatings in various embodiments of this invention. In certain example embodiments, the crystalline or substantially crystalline layer 3 and/or 13 of or including zinc oxide is doped with from about 1-30% Sn, more preferably from about 1-20% Sn, more preferably from about 5-15% Sn, with an example being about 10% Sn (in terms of wt. %). The zinc oxide, doped with Sn, is in a crystallized or substantially crystallized phase (as opposed to amorphous or nanocrystalline) in layer 3 and/or 13 as deposited, such as via sputter deposition techniques from at least one sputtering target(s) of or including Zn and Sn. The crystallized phase of the doped zinc oxide based layer 3 and/or 13 as deposited, combined with the layer(s) between the silver 7 and/or 19 and the glass 1, allows the coated article to realize improved thermal stability upon optional HT (lower the ΔE* value). It is believed that the crystallized phase of the doped zinc oxide based layer 3 and/or 13 as deposited, combined with the layer(s) between the silver and the glass, allows the silver 7 and/or 19 deposited thereover to have improved crystal structure with texture but with some randomly oriented grains so that its refractive index (n) changes less upon optional HT, thereby allowing for improved thermal stability to be realized.

In certain example embodiments, it has also been surprisingly and unexpectedly found that the provision of a dielectric layer 2 of or including silicon zirconium oxide and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, and/or SiZrO_(x)N_(y)) under and directly contacting the doped zinc oxide based layer 3, such as shown in FIGS. 1(b)-1(d) for example, provides for further improved thermal stability of the coated article, and thus even lower the ΔE* values upon heat treatment (HT) such as thermal tempering. The dielectric layer 2 of or including silicon zirconium oxide and/or silicon zirconium oxynitride (e.g., SiZrO_(x) and/or SiZrO_(x)N_(y)) may be provided directly under and contacting the lowermost doped zinc oxide based layer 3 in certain example embodiments of this invention.

It has also been surprisingly and unexpectedly found that the provision of no silicon nitride based layer (e.g., Si₃N₄, optionally doped with 1-10% Al or the like) directly under and contacting the lowermost doped zinc oxide based layer 3 between the glass substrate 1 and the lowermost silver based layer 7, in combination with the crystallized or substantially crystallized phase of the doped zinc oxide based layer 3 as deposited, allows for improved thermal stability upon heat treatment (lower ΔE* values) to be realized. For example, see the coatings of FIGS. 1(a)-1(d). Moreover, in certain example embodiments, there is no amorphous or substantially amorphous layer located between the glass substrate 1 and the first IR reflecting layer comprising silver 7.

In certain example embodiments, it has also surprisingly and unexpectedly been found that providing an absorber layer (e.g., NiCr, NiCrN_(x), NbZr, and/or NbZrN_(x)) 42 between the glass substrate and the dielectric layer 2 of or including silicon zirconium oxide and/or silicon zirconium oxynitride (e.g., SiZrO_(x) and/or SiZrO_(x)N_(y)) advantageously reduces glass side visible reflection (R_(g)Y) of the coated article in a desirable manner and allows the visible transmission to be tuned in a desirable manner. The absorber layer 42 may be provided between and contacting a pair of silicon nitride based layers 41 and 43 (e.g., of or including Si₃N₄, optionally doped with 1-10% Al or the like, and optionally including from 0-10% oxygen) in certain example embodiments, such as shown in FIG. 1(d) for instance.

In certain example embodiments, measured monolithically, in view of the above structure (e.g., see FIGS. 1(a)-1(d)), the coated article is configured to realize one or more of: (i) a transmissive ΔE* value (where transmissive optics are measured) of no greater than 3.0 (more preferably no greater than 2.5, and most preferably no greater than 2.3) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value (where glass side reflective optics are measured) of no greater than 3.0 (more preferably no greater than 2.0, and most preferably no greater than 1.0) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C., and/or (iii) a film side reflective ΔE* value (where film side reflective optics are measured) of no greater than 3.5 (more preferably no greater than 3.0, and most preferably no greater than 2.0) upon HT for 8, 12 and/or 16 minutes at a temperature of about 650 degrees C.

In certain example embodiments, measured monolithically, the coated article is configured to have a visible transmission (T_(vis) or Y), before or after any optional HT, of at least about 50%, more preferably of at least about 60%, and most preferably of at least about 68% or 70%. In certain example embodiments, the low-E coating has a sheet resistance (SR or R_(s)) of no greater than 20 ohms/square, more preferably no greater than 10 ohms/square, and most preferably no greater than 2.2 ohms/square, before and/or after optional heat treatment. In certain example embodiments, the low-E coating has a hemispherical emissivity/emittance (E_(h)) of no greater than 0.08, more preferably no greater than 0.05, and most preferably no greater than 0.04.

The value ΔE* is important in determining whether or not upon heat treatment (HT) there is matchability, or substantial matchability, in the context of this invention. Color herein is described by reference to the conventional a*, b* values, which in certain embodiments of this invention are both negative in order to provide color in the desired substantially neutral color range tending to the blue-green quadrant. For purposes of example, the term Δa* is simply indicative of how much color value a* changes due to heat treatment.

The term ΔE* (and AE) is well understood in the art and is reported, along with various techniques for determining it, in ASTM 2244-93 as well as being reported in Hunter et. al., The Measurement of Appearance, 2^(nd) Ed. Cptr. 9, page 162 et seq. [John Wiley & Sons, 1987]. As used in the art, ΔE* (and ΔE) is a way of adequately expressing the change (or lack thereof) in reflectance and/or transmittance (and thus color appearance, as well) in an article after or due to heat treatment. ΔE may be calculated by the “ab” technique, or by the Hunter technique (designated by employing a subscript “H”). ΔE corresponds to the Hunter Lab L, a, b scale (or L_(h), a_(h), b_(h)). Similarly, ΔE* corresponds to the CIE LAB Scale L*, a*, b*. Both are deemed useful, and equivalent for the purposes of this invention. For example, as reported in Hunter et. al. referenced above, the rectangular coordinate/scale technique (CIE LAB 1976) known as the L*, a*, b* scale may be used, wherein:

-   -   L* is (CIE 1976) lightness units     -   a* is (CIE 1976) red-green units     -   b* is (CIE 1976) yellow-blue units

and the distance ΔE* between L*_(o) a*_(o) b*_(o) and L*₁ a*₁ b*₁ is: ΔE*=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2)  (1) where:

$\begin{matrix} {{\Delta\; L^{*}} = {L_{1}^{*} - L_{o}^{*}}} & (2) \\ {{\Delta\; a^{*}} = {a_{1}^{*} - a_{o}^{*}}} & (3) \\ {{\Delta\; b^{*}} = {b_{1}^{*} - b_{o}^{*}}} & (4) \end{matrix}$ where the subscript “o” represents the coated article before heat treatment and the subscript “1” represents the coated article after heat treatment; and the numbers employed (e.g., a*, b*, L*) are those calculated by the aforesaid (CIE LAB 1976) L*, a*, b* coordinate technique. In a similar manner, ΔE may be calculated using equation (1) by replacing a*, b*, L* with Hunter Lab values a_(h), b_(h), L_(h). Also within the scope of this invention and the quantification of ΔE* are the equivalent numbers if converted to those calculated by any other technique employing the same concept of ΔE* as defined above.

In certain example embodiments of this invention, the low-E coating 30 includes a double-silver stack (e.g., see FIGS. 1(a)-1(d)), although this invention is not so limited in all instances (e.g., three silver based layers can be used in certain instances, or alternatively a single silver stack may be used). It will be recognized that the coated articles of FIGS. 1(a)-1(d) are illustrated in monolithic form. However, these coated articles may also be used in IG window units for example.

Because of materials stability, baking at high temperature (e.g., 580-650 degrees C.) causes change to chemical compositions, crystallinity and microstructures or even phases of dielectric layer materials. High temperature also causes interface diffusion or even reaction, as a consequence composition, roughness and index change at interface locations. As a result, optical properties such as index n/k and optical thickness change upon heat treatment. The IR materials, for example Ag, have undergo change too. Typically, Ag materials go through crystallization, grain growth or even orientation change upon heat treatment. These changes often cause conductivity and particularly index n/k changes which have big impact to the optical and thermal properties of a low-E coating. In addition, the dielectric and the change of dielectrics also has a significant impact on IR reflecting layers such as silver undergoing heat treatment. Moreover, silver may have more change in one layer stack than in others merely because of the materials and the layer stacks themselves. If the silver changes are beyond some limit, then it may not be acceptable aesthetically after heat treatment. We have found that to get thermal stability of a low-E coating, doped zinc oxide crystallized materials on glass either directly or indirectly with a thin modification layer(s) may be used under silver. Crystalline or substantially crystalline doped zinc oxide in these locations has been found to change less during heat treatment, and result in smaller silver changes with respect to properties such as indices (e.g., n and/or k) and thus less overall color change upon heat treatment.

FIG. 1(a) is a side cross sectional view of a coated article according to an example non-limiting embodiment of this invention, where the low-E coating 30 has two silver-based IR reflecting layers 7 and 19. The coated article includes substrate 1 (e.g., clear, green, bronze, or blue-green glass substrate from about 1.0 to 10.0 mm thick, more preferably from about 3.0 mm to 8.0 mm thick), and low-E coating (or layer system) 30 provided on the substrate 1 either directly or indirectly. The coating (or layer system) 30 includes, in FIG. 1(a) for example: dielectric layer 3 of or including zinc oxide, doped with at least one metal dopant (e.g., Sn and/or Al), which is crystalline or substantially crystalline as deposited; infrared (IR) reflecting layer of or including silver 7 located over and directly contacting layer 3; contact layer 9 of or including Ni and/or Cr (e.g., NiCr, NiCrO_(x), NiCrN_(x), NiCrON, NiCrM, NiCrMoO_(x), etc.), Ti, or other suitable material, over and directly contacting the IR reflecting layer 7; dielectric layer 11 of or including zinc stannate (e.g., ZnSnO, Zn₂SnO₄, or other suitable stoichiometry) or other suitable material, which may be amorphous or substantially amorphous as deposited; another dielectric layer 13 of or including zinc oxide, doped with at least one dopant (e.g., Sn), which is crystalline or substantially crystalline as deposited; another infrared (IR) reflecting layer of or including silver 19 located over and directly contacting layer 13; another contact layer 21 of or including Ni and/or Cr (e.g., NiCr, NiCrO_(x), NiCrN_(x), NiCrON, NiCrM, NiCrMoO_(x), etc.), Ti, or other suitable material, over and directly contacting the IR reflecting layer 19; another dielectric layer 23 of or including zinc stannate (e.g., ZnSnO, Zn₂SnO₄, or other suitable stoichiometry) or other suitable material such as tin oxide, which may be amorphous or substantially amorphous as deposited; and amorphous or substantially amorphous dielectric layer 25 of or including silicon nitride (e.g., Si₃N₄, or other suitable stoichiometry) which may optionally be doped with Al and/or O. The layers shown in FIG. 1(a) may be deposited by sputter-deposition or in any other suitable manner.

As explained herein, it has been found that the presence of as-deposited crystalline or substantially crystalline layer 3 and/or 13 of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under and directly contacting an infrared (IR) reflecting layer of or including silver 7 and/or 19 in a low-E coating 30 has the effect of significantly improving the coating's thermal stability (i.e., lowering the ΔE* value). In certain example embodiments, the crystalline or substantially crystalline layer 3 and/or 13 of or including zinc oxide is doped with from about 1-30% Sn, more preferably from about 1-20% Sn, more preferably from about 5-15% Sn, with an example being about 10% Sn (in terms of wt. %).

In certain example embodiments, the dielectric zinc stannate (e.g., ZnSnO, Zn₂SnO₄, or the like) based layers 11 and 23 may be deposited in an amorphous or substantially amorphous state (it/they may become crystalline or substantially crystalline upon heat treatment). It has been found that having similar amounts of Zn and Sn in the layer, or more Sn than Zn in the layer, helps ensure that the layer is deposited in an amorphous or substantially amorphous state. For example, the metal content of amorphous zinc stannate based layers 11 and 23 may include from about 30-70% Zn and from about 30-70% Sn, more preferably from about 40-60% Zn and from about 40-60% Sn, with examples being about 52% Zn and about 48% Sn, or about 50% Zn and 50% Sn (weight %, in addition to the oxygen in the layer) in certain example embodiments of this invention. Thus, for example, the amorphous or substantially amorphous zinc stannate based layers 11 and/or 23 may be sputter-deposited using a metal target comprising about 52% Zn and about 48% Sn, or about 50% Zn and about 50% Sn, in certain example embodiments of this invention. Optionally, the zinc stannate based layers 11 and 23 may be doped with other metals such as Al or the like. Depositing layers 11 and 23 in an amorphous, or substantially amorphous, state, while depositing layers 3 and 13 in a crystalline, or substantially crystalline, state, has been found to advantageously allow for improved thermal stability to be realized in combination with good optical characteristics such as acceptable transmission, color, and reflection. It is noted that zinc stannate layers 11 and/or 23 may be replaced with respective layer(s) of other material(s) such as tin oxide, or the like.

Dielectric layer 25, which may be an overcoat, may be of or include silicon nitride (e.g., Si₃N₄, or other suitable stoichiometry) in certain embodiments of this invention, in order to improve the heat treatability and/or durability of the coated article. The silicon nitride may optionally be doped with Al and/or O in certain example embodiments, and also may be replaced with other material such as silicon oxide or zirconium oxide in certain example embodiments.

Infrared (IR) reflecting layers 7 and 19 are preferably substantially or entirely metallic and/or conductive, and may comprise or consist essentially of silver (Ag), gold, or any other suitable IR reflecting material. IR reflecting layers 7 and 19 help allow the coating to have low-E and/or good solar control characteristics. The IR reflecting layers may, however, be slightly oxidized in certain embodiments of this invention.

Other layer(s) below or above the illustrated coating in FIG. 1 may also be provided. Thus, while the layer system or coating is “on” or “supported by” substrate 1 (directly or indirectly), other layer(s) may be provided therebetween. Thus, for example, the coating of FIG. 1(a) may be considered “on” and “supported by” the substrate 1 even if other layer(s) are provided between layer 3 and substrate 1. Moreover, certain layers of the illustrated coating may be removed in certain embodiments, while other layer(s) may be added between the various layers or the various layer(s) may be split with other layer(s) added between the split sections in other embodiments of this invention without departing from the overall spirit of certain embodiments of this invention.

While various thicknesses and materials may be used in layers in different embodiments of this invention, example thicknesses and materials for the respective layers on the glass substrate 1 in the FIG. 1(a) embodiment are as follows, from the glass substrate outwardly:

TABLE 1 Example Materials/Thicknesses; FIG. 1(a) Embodiment Layer More Example Glass Preferred Range ({acute over (Å)}) Preferred ({acute over (Å)}) (Å) Sn-doped ZnO 20-900 (or 100-900) {acute over (Å)} 350-550 {acute over (Å)} 470 Å (layer 3) Ag (layer 7) 60-260 {acute over (Å)} 110-170 {acute over (Å)} 151 Å NiCrO_(x) (layer 9) 10-100 {acute over (Å)} 20-45 {acute over (Å)}  41 Å ZnSnO (layer 11) 200-1200 {acute over (Å)} 500-900 {acute over (Å)} 736 Å Sn-doped ZnO 60-900 {acute over (Å)} 120-400 {acute over (Å)} 177 Å (layer 13) Ag (layer 19) 80-280 {acute over (Å)} 150-250 {acute over (Å)} 232 Å NiCrO_(x) (layer 21) 10-100 {acute over (Å)} 20-45 {acute over (Å)}  41 Å ZnSnO (layer 23) 10-750 {acute over (Å)} 70-200 {acute over (Å)} 108 Å Si₃N₄ (layer 25) 10-750 {acute over (Å)} 100-240 {acute over (Å)} 191 Å

The FIG. 1(b) embodiment is the same as the FIG. 1(a) embodiment discussed above and elsewhere herein, except that the low-E coating 30 in the FIG. 1(b) embodiment also includes a substantially transparent dielectric layer 2 of or including silicon zirconium oxide, zirconium oxide, silicon oxide, and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, SiO₂, SiAlO₂, and/or SiZrO_(x)N_(y)) under and directly contacting the doped zinc oxide based layer 3. It has been found that this additional layer 2 provides for further improved thermal stability of the coated article, and thus an even lower the ΔE* value (e.g., a lower glass side reflective ΔE* value) upon heat treatment (HT) such as thermal tempering. The dielectric layer 2 of or including silicon zirconium oxide, zirconium oxide, silicon oxide, and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, SiO₂, SiAlO₂, and/or SiZrO_(x)N_(y)) may be provided directly under and contacting the lowermost doped zinc oxide based layer 3 in certain example embodiments of this invention, as shown in FIG. 1(b). In certain example embodiments of this invention, dielectric layer 2 of or including silicon zirconium oxide, zirconium oxide, silicon oxide, and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, SiO₂, SiAlO₂, and/or SiZrO_(x)N_(y)) may be from about 20-600 Å thick, more preferably from about 40-400 Å thick, and most preferably from about 50-300 Å thick. The thicknesses above for the FIG. 1(a) embodiment may also apply to FIGS. 1(b)-1(d).

When layer 2 is of or includes SiZrO_(x) and/or SiZrO_(x)N_(y), it has been found that providing more Si than Zr in that layer is advantageous from an optical point of view with a low refractive index (n) and improved antireflection and other optical characteristics. For example, in certain example embodiments, when layer 2 is of or includes SiZrO_(x) and/or SiZrO_(x)N_(y), metal content of the layer may comprise from 51-99% Si, more preferably from 70-97% Si, and most preferably from 80-90% Si, and from 1-49% Zr, more preferably from 3-30% Zr, and most preferably from 10-20% Zr (atomic %). In example embodiments, transparent dielectric layer 2 of or including SiZrO_(x) and/or SiZrO_(x)N_(y) may have a refractive index (n), measured at 550 nm, of from about 1.48 to 1.68, more preferably from about 1.50 to 1.65, and most preferably from about 1.50 to 1.62.

The FIG. 1(c) embodiment is the same as the FIG. 1(b) embodiment discussed above and elsewhere herein, except that the low-E coating 30 in the FIG. 1(c) embodiment also includes a substantially transparent dielectric layer 2′ of or including silicon nitride (e.g., Si₃N₄, optionally doped with 1-10% Al or the like, and optionally including from 0-10% oxygen, or other suitable stoichiometry) and/or silicon zirconium oxynitride, located between and contacting the glass substrate 1 and the dielectric layer 2.

The FIG. 1(d) embodiment is the same as the FIG. 1(b) embodiment discussed above and elsewhere herein, except that the low-E coating 30 in the FIG. 1(d) embodiment also includes a metallic or substantially metallic absorber layer 42 sandwiched between and contacting silicon nitride based layers 41 and 43 (e.g., Si₃N₄, optionally doped with 1-10% Al or the like, and optionally including from 0-10% oxygen). The absorber layer 42 may be of or including NiCr, NbZr, Nb, Zr, or nitrides thereof, in example embodiments of this invention. The absorber layer 42 preferably contains from 0-10% oxygen (atomic %), more preferably from 0-5% oxygen. In certain example embodiments, it has surprisingly and unexpectedly been found that providing an absorber layer (e.g., NiCr, NiCrN_(x), NbZr, and/or NbZrN_(x)) 42 between the glass substrate and the dielectric layer 2 of or including silicon zirconium oxide, zirconium oxide, silicon oxide, and/or silicon zirconium oxynitride (e.g., SiZrO_(x), ZrO₂, SiO₂, SiAlO₂, and/or SiZrO_(x)N_(y)) advantageously reduces glass side visible reflection (R_(g)Y) of the coated article in a desirable manner, and allows the visible transmission to be tuned in a desirable manner. In certain example embodiments, the absorber layer 42 may be from about 10-150 Å thick, more preferably from about 30-80 Å thick. In certain example embodiments, the silicon nitride based layers 41 and 43 may be from about 50-300 Å thick, more preferably from about 70-140 Å thick.

Referring to FIGS. 1(a)-1(d), another transparent dielectric layer (not shown) of or including ZrO₂, SiZrO_(x) and/or SiZrO_(x)N_(y) may be provided either between layers 11 and 13. In certain example embodiments, zinc stannate inclusive layer 11 may be omitted, or may be replaced with such another transparent dielectric layer of or including ZrO₂, SiZrO_(x) and/or SiZrO_(x)N_(y). It is also possible for doped zinc oxide layer 13 to be split with such another layer transparent dielectric layer of or including ZrO₂, SiZrO_(x) and/or SiZrO_(x)N_(y). For example, in certain example embodiments, when such an additional layer is of or includes SiZrO_(x) and/or SiZrO_(x)N_(y), metal content of the layer may comprise from 51-99% Si, more preferably from 70-97% Si, and most preferably from 80-90% Si, and from 1-49% Zr, more preferably from 3-30% Zr, and most preferably from 10-20% Zr (atomic %), and may contain from 0-20% nitrogen, more preferably from 0-10% nitrogen, and most preferably from 0-5% nitrogen (atomic %).

As explained above and shown in the figures, the coated article may include a dielectric layer(s) 2 as shown in FIGS. 1(b)-(d), located under and directly contacting the first crystalline or substantially crystalline layer 3 comprising zinc oxide doped with from about 1-30% Sn. The dielectric layer(s) 2 may comprise one or more of ZrO₂, SiO₂ which may optionally be doped with from 1-10% Al, and/or an oxide of silicon and zirconium. The dielectric layer 2 may be in direct contact with the glass substrate 1. The dielectric layer(s) 2 may have a physical thickness of from about 40-400 Å, more preferably from about 50-300 Å, and most preferably from about 50-200 Å. The dielectric layer(s) 2 is preferably an oxide based dielectric layer, and preferably contains little or no nitrogen. For example, the dielectric layer(s) 2 (both the illustrated layer 2, and the possible additional such layer discussed above) may comprise from 0-20% nitrogen, more preferably from 0-10% nitrogen, and most preferably from 0-5% nitrogen (atomic %).

In certain embodiments of this invention, layer systems herein (e.g., see FIGS. 1(a)-(d)) provided on clear monolithic glass substrates (e.g., 6 mm thick glass substrates for example reference purposes) have color as follows before heat treatment, as viewed from the glass side of the coated article (R_(G) %) (Ill. C, 2 degree Observer):

TABLE 2 Reflection/Color (R_(G)) Before and/or After Heat Treatment General Preferred R_(g)Y (%) 7-18% 8-14% a_(g)* −5.0 to +4.0 −3.0 to +2.0 b_(g)* −16.0 to 0.0  −14.0 to −5.0 

COMPARATIVE EXAMPLES 1 AND 2

FIG. 19 is a cross sectional view of a first Comparative Example (CE) coated article, and FIG. 23 is an XRD Lin (Cps) vs. 2-Theta-Scale graph illustrating, for the first Comparative Example (CE), the relative large 166% change in Ag (111) peak height due to heat treatment.

The difference between the first Comparative Example coating (see FIG. 19), and Examples 1-18 below, is that the lowermost dielectric stack of the coating in the first Comparative Example is made up of a Zn₂SnO₄ layer, and a zinc oxide based layer that is doped with aluminum. The metal content of the zinc stannate layer (Zn₂SnO₄ is a form of zinc stannate) is about 50% Zn and about 50% Sn (wt. %); and thus the zinc stannate layer is sputter-deposited in amorphous form. The overall thickness of the lowermost dielectric stack in the first CE was about 400-500 angstroms, with the zinc stannate layer making up the majority of that thickness. FIG. 23 illustrates, for the first Comparative Example (CE), the relative large 166% change in Ag (111) peak height due to heat treatment at about 650 degrees C. which is indicative of a significant change in structure of the silver layers during the heat treatment, and which is consistent with the of ΔE* values over 4.0 realized by the Comparative Example. Thus, the first CE was undesirable because of the significant changes in the Ag (111) peak, and the high of ΔE* values over 4.0, due to heat treatment.

A second Comparative Example (CE 2) is shown in FIGS. 34-35. FIG. 34 is chart illustrating sputter-deposition conditions for the sputter-deposition of the low-E coating of Comparative Example 2 (CE 2) on a 6 mm thick glass substrate. The layer stack of CE 2 is the same as that shown in FIG. 1(b) of the instant application, except that the lowermost dielectric layer in CE 2 is made of silicon nitride (doped with about 8% aluminum) instead of the SiZrO_(x) shown in FIG. 1(b). Thus, the bottom dielectric stack in CE 2 is made up of only this silicon nitride based layer and a zinc oxide layer 3 doped with about 10% Sn. The thicknesses of the layers of the coating of CE 2 are in the far right column of FIG. 34. For example, the bottom silicon nitride based layer, doped with Al (sputtered from an SiAl target in an atmosphere of Ar and N₂ gas), is 10.5 nm thick in CE 2, the zinc oxide layer 3 doped with about 10% Sn directly under the bottom silver is 32.6 nm thick in CE 2, and so forth.

It can be seen in FIG. 35 that CE 2 suffers from relatively high glass side reflective ΔE* values (ΔE* R_(g)) and film side reflective ΔE* values (ΔE* R_(f)) over 4.0, due to heat treatments of 12, 16, and 24 minutes. For example, FIG. 35 shows that CE has a relatively high glass side reflective ΔE* value (ΔE* R_(g)) of 4.9 and a relatively high film side reflective ΔE* value (ΔE* R_(f)) of 5.5 due to heat treatment for 12 minutes. FIG. 35 is a chart illustrating optical characteristics of Comparative Example 2 (CE 2): as coated (annealed) before heat treatment in the left-most data column, after 12 minutes of heat treatment at 650 degrees C. (HT), after 16 minutes of HT at 650 degrees C. (HTX), and after 24 minutes of heat treatment at 650 degrees C. (HTXXX) in the far right data column. There relatively high ΔE* values of CE 2 are undesirable.

Accordingly, Comparative Example 2 (CE 2) in FIGS. 34-35 demonstrates that undesirably high ΔE* values are realized, even when a crystalline or substantially crystalline zinc oxide layer 3 doped with about 10% Sn is provided directly below the bottom silver layer 7, when the only layer between that layer 3 and the glass substrate 1 is a silicon nitride based layer. The difference between the CE 2 coating, and Examples 1-18 below, is that Examples 1-18 below were surprisingly and unexpectedly able to realize much improved (lower) ΔE* values using the crystalline or substantially crystalline zinc oxide layer 3 doped with about 10% Sn, by not having a silicon nitride based layer located directly below and contacting the crystalline or substantially crystalline zinc oxide layer 3 doped with about 10% Sn.

EXAMPLES 1-18

Surprisingly and unexpectedly, it was found that when the lowermost dielectric stack 5, 6 of the Comparative Example (CE) (made up mostly by the zinc stannate layer which is amorphous as deposited) in FIG. 19 was replaced with a crystalline or substantially crystalline Sn-doped zinc oxide layer 3 of similar thickness (the rest of the stack remained substantially the same) contacting the silver based layer, with no silicon nitride based layer directly under and contacting the crystalline or substantially crystalline layer 3, the result was a much more thermally stable product with significant lower ΔE* values and a much smaller change in Ag (111) peak height due to heat treatment at about 650 degrees C. The metal content of the crystalline or substantially crystalline Sn-doped zinc oxide layer 3 in Examples 1-18 was approximately 90% Zn and 10% Sn (wt. %), which helped allow the Sn-doped zinc oxide layers in Examples 1-18 to be sputter-deposited in crystalline or substantially crystalline form (as opposed to the amorphous form in the CE). For instance, FIG. 20 illustrates the layer stack of Example 10, FIG. 21 illustrates the sputter-deposition conditions and layer thicknesses of Example 10, and FIG. 22 illustrates the much smaller 66% change in Ag (111) peak height due to heat treatment at about 650 degrees C. for Example 10 which is consistent with the much lower ΔE* values realized by Examples 1-18. FIG. 16 also illustrates the relatively small refractive index (n) shift, upon heat treatment, for Example 8.

The Example coated articles (each annealed and heat treated), Examples 1-18, were made in accordance with certain example embodiments of this invention. Indicated example coatings 30 were sputter-deposited via the sputtering conditions (e.g., gas flows, voltage, and power), sputtering targets, and to the layer thicknesses (nm) shown in FIGS. 2, 3, 6, 7, 9, 11, 13, 15, 21, 24-26, 28, 30 and 32. For example, FIG. 2 shows the sputtering conditions, sputtering targets used for sputter-depositing, and the layer thicknesses for the coating of Example 1, FIG. 3 shows the sputtering conditions, sputtering targets used for sputter-depositing, and the layer thicknesses for the coating of Example 2, FIG. 6 shows the sputtering conditions, sputtering targets used for sputter-depositing, and the layer thicknesses for the coating of Example 3, FIG. 7 shows the sputtering conditions, sputtering targets used for sputter-depositing, and the layer thicknesses for the coating of Example 4, and so forth. Meanwhile, data for the indicated Examples, including visible transmission (TY or T_(vis)), glass side visible reflectance (R_(g)Y), film side visible reflectance (R_(f)Y), a* and b* color values, L* values, and sheet resistance (SR or R_(s)) are shown in FIGS. 4, 5, 8, 10, 12, 14, 18, 27, 29, 31 and 33. As explained above, ΔE* values are calculated using the L*, a*, and b* values, taken before and after heat treatment, for a given example. For instance, a glass side reflective ΔE* value (ΔE* R_(g)) is calculated using the glass side reflective L*, a*, and b* values, taken before and after heat treatment, for a given example.

For examples having approximately 3 mm thick glass substrates, in FIGS. 4, 5, 8, 10, 12, 14, and 18, “HT” refers to heat treatment at 650 degrees for about 8 minutes, “HTX” refers to heat treatment at 650 degrees for about 12 minutes, and “HTXXX” refers to heat treatment at 650 degrees for about 20 minutes. And for examples having approximately 6 mm thick glass substrates, in FIGS. 4, 5, 8, 10, 12, 14, 18, 27, 29, 31, and 33, “HT” refers to heat treatment at 650 degrees for about 12 minutes, “HTX” refers to heat treatment at 650 degrees for about 16 minutes, and “HTXXX” refers to heat treatment at 650 degrees for about 24 minutes. The heat treatment temperatures and times are for reference purposes only (e.g., to simulate examples of different tempering and/or heat bending processes).

FIGS. 4 and 5, for instance, illustrate the ΔE* values for Examples 1 and 2, respectively. The data for Example 1 is explained below in detail, for purposes of example and explanation, and that discussion also applies to the data for Examples 2-18.

As shown in FIG. 4, Example 1 as coated (prior to heat treatment) had a visible transmission (TY or T_(vis)) of 74.7%, a transmissive L* value of 89.3, a transmissive a* color value of −4.7, a transmissive b* color value of 5.8, a glass side reflectance (R_(g)Y) of 9.6%, a glass side reflective L* value of 37.1, a glass side reflective a* color value of −1.1, a glass side reflective b* color value of −10.1, a film side reflectance (R_(f)Y) of 9.9%, a film side reflective L* value of 37.7, a film side reflective a* color value of −1.5, a film side reflective b* color value of −5.7, and a sheet resistance (SR) of 2.09 ohms/square. FIG. 2 shows the thicknesses of the layers in Example 1. In particular, FIG. 2 shows that the layer thicknesses for Example 1 were are follows: glass/crystalline Sn-doped ZnO(47.0 nm)/Ag(15.1 nm)/NiCrO_(x) (4.1 nm)/amorphous zinc stannate(73.6 nm)/crystalline Sn-doped ZnO(17.7 nm)/Ag(23.2 nm)/NiCrO_(x) (4.1 nm)/amorphous zinc stannate(10.8 nm)/silicon nitride doped with aluminum (19.1 nm).

The coated article of Example 1, which had a 6 mm thick glass substrate 1, was then heat treated. As shown in FIG. 4, Example 1 following heat treatment at 650 degrees C. for about 12 minutes had a visible transmission (TY or T_(vis)) of 77.0%, a transmissive L* value of 90.3, a transmissive a* color value of −3.5, a transmissive b* color value of 4.9, a glass side reflectance (R_(g)Y) of 9.8%, a glass side reflective L* value of 37.5, a glass side reflective a* color value of −0.7, a glass side reflective b* color value of −10.5, a film side reflectance (R_(f)Y) of 10.2%, a film side reflective L* value of 38.1, a film side reflective a* color value of −1.4, a film side reflective b* color value of −8.0, a sheet resistance (SR) of 1.75, a transmissive ΔE* value of 1.8, a glass side reflective ΔE* value 0.7, and a film side reflective ΔE* value of 2.4.

It will be appreciated that these ΔE* values for Example 1 (and also those for Examples 2-18) are much improved (significantly lower) than those of the prior art discussed in the background and compared to the values over 4.0 for the Comparative Examples (CEs) discussed above. Thus, the data from the examples demonstrates that when the lowermost dielectric stacks of the Comparative Examples was replaced with at least a crystalline or substantially crystalline Sn-doped zinc oxide layer of similar thickness (the rest of the stack remained substantially the same), with no silicon nitride based layer directly under and contacting the crystalline or substantially crystalline Sn-doped zinc oxide layer 3, the result was a much more thermally stable product with significant lower ΔE* values and a much smaller change in Ag (111) peak height due to heat treatment.

The other examples show these same unexpected results, compared to the Comparative Example. For example, Examples 1-10 had layer stacks generally shown by FIG. 1(a) where the only dielectric layer beneath the bottom silver was the crystalline or substantially crystalline Sn-doped zinc oxide layer 3 with a metal content of approximately 90% Zn and 10% Sn (wt. %); in Examples 11-14 metal content of the crystalline or substantially crystalline Sn-doped zinc oxide layer 3 was approximately 90% Zn and 10% Sn (wt. %), directly over a SiZrO_(x) layer 2 where metal content of the layer 2 was about 85% Si and 15% Zr (atomic %); in Examples 15-16 metal content of the crystalline or substantially crystalline Sn-doped zinc oxide layer 3 was approximately 90% Zn and 10% Sn (wt. %), directly over a ZrO₂ layer 2; and in Examples 17-18 metal content of the crystalline or substantially crystalline Sn-doped zinc oxide layer 3 was approximately 90% Zn and 10% Sn (wt. %), directly over a SiO₂ layer 2 doped with about 8% Al (atomic %). These examples surprisingly and unexpectedly realized much improved ΔE* values compared to the Comparative Examples.

Certain terms are prevalently used in the glass coating art, particularly when defining the properties and solar management characteristics of coated glass. Such terms are used herein in accordance with their well known meaning. For example, as used herein:

Intensity of reflected visible wavelength light, i.e. “reflectance” is defined by its percentage and is reported as R_(x)Y or R_(x) (i.e. the Y value cited below in ASTM E-308-85), wherein “X” is either “G” for glass side or “F” for film side. “Glass side” (e.g. “G” or “g”) means, as viewed from the side of the glass substrate opposite that on which the coating resides, while “film side” (i.e. “F” or “f”) means, as viewed from the side of the glass substrate on which the coating resides.

Color characteristics are measured and reported herein using the CIE LAB a*, b* coordinates and scale (i.e. the CIE a*b* diagram, Ill. CIE-C, 2 degree observer). Other similar coordinates may be equivalently used such as by the subscript “h” to signify the conventional use of the Hunter Lab Scale, or Ill. CIE-C, 10⁰ observer, or the CIE LUV u*v* coordinates. These scales are defined herein according to ASTM D-2244-93 “Standard Test Method for Calculation of Color Differences From Instrumentally Measured Color Coordinates” Sep. 15, 1993 as augmented by ASTM E-308-85, Annual Book of ASTM Standards, Vol. 06.01 “Standard Method for Computing the Colors of Objects by 10 Using the CIE System” and/or as reported in IES LIGHTING HANDBOOK 1981 Reference Volume.

Visible transmittance can be measured using known, conventional techniques. For example, by using a spectrophotometer, such as a Perkin Elmer Lambda 900 or Hitachi U4001, a spectral curve of transmission is obtained. Visible transmission is then calculated using the aforesaid ASTM 308/2244-93 methodology. A lesser number of wavelength points may be employed than prescribed, if desired. Another technique for measuring visible transmittance is to employ a spectrometer such as a commercially available Spectrogard spectrophotometer manufactured by Pacific Scientific Corporation. This device measures and reports visible transmittance directly. As reported and measured herein, visible transmittance (i.e. the Y value in the CIE tristimulus system, ASTM E-308-85), as well as the a*, b*, and L* values, and glass/film side reflectance values, herein use the Ill. C.,2 degree observer standard.

Another term employed herein is “sheet resistance”. Sheet resistance (R_(s)) is a well known term in the art and is used herein in accordance with its well known meaning. It is here reported in ohms per square units. Generally speaking, this term refers to the resistance in ohms for any square of a layer system on a glass substrate to an electric current passed through the layer system. Sheet resistance is an indication of how well the layer or layer system is reflecting infrared energy, and is thus often used along with emittance as a measure of this characteristic. “Sheet resistance” may for example be conveniently measured by using a 4-point probe ohmmeter, such as a dispensable 4-point resistivity probe with a Magnetron Instruments Corp. head, Model M-800 produced by Signatone Corp. of Santa Clara, Calif.

The terms “heat treatment” and “heat treating” as used herein mean heating the article to a temperature sufficient to achieve thermal tempering, heat bending, and/or heat strengthening of the glass inclusive coated article. This definition includes, for example, heating a coated article in an oven or furnace at a temperature of least about 580 degrees C., more preferably at least about 600 degrees C., including 650 degrees C., for a sufficient period to allow tempering, bending, and/or heat strengthening. In certain instances, the heat treatment may be for at least about 8 minutes or more as discussed herein.

In an example embodiment of this invention, there is provided a coated article including a coating on a glass substrate, wherein the coating comprises: a first crystalline or substantially crystalline layer (e.g., at least 50% crystalline, more preferably at least 60% crystalline) comprising zinc oxide doped with from about 1-30% Sn (wt. %), provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn; wherein no silicon nitride based layer (which includes no silicon oxynitride based layer) is located directly under and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn between the glass substrate and the first IR reflecting layer comprising silver; and wherein the coated article is configured to have, measured monolithically, one, two, or all three of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C. (e.g., on a reference 3 mm thick glass substrate), (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C. (e.g., on a reference 3 mm thick glass substrate), and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C. (e.g., on a reference 3 mm thick glass substrate).

In the coated article of the immediately preceding paragraph, the first crystalline or substantially crystalline layer comprising zinc oxide may be doped with from about 1-20% Sn (wt. %), more preferably with from about 5-15% Sn (wt. %), and most preferably with about 10% Sn (wt. %).

In the coated article of any of the preceding two paragraphs, the first crystalline or substantially crystalline layer comprising zinc oxide doped with Sn may be crystalline or substantially crystalline as sputter-deposited.

In the coated article of any of the preceding three paragraphs, the coated article may be configured to have, measured monolithically, at least two of: (i) a transmissive ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding four paragraphs, the coated article may be configured to have, measured monolithically, all of: (i) a transmissive ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding five paragraphs, the coated article may be configured to have, measured monolithically, at least two of: (i) a transmissive ΔE* value of no greater than 2.5 due to a reference heat treatment for 12 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding six paragraphs, the coated article may be configured to have, measured monolithically, all of: (i) a transmissive ΔE* value of no greater than 2.5 due to a reference heat treatment for 12 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding seven paragraphs, the coated article may be configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 2.3 due to a reference heat treatment for 16 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 1.0 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding eight paragraphs, the coating may have a sheet resistance (R_(s)) of no greater than 20 ohms/square, more preferably no greater than 10 ohms/square, and most preferably no greater than 2.2 ohms/square, before and/or after heat treatment.

In the coated article of any of the preceding nine paragraphs, the coated article may have a visible transmission of at least 50%, more preferably of at least 60%, and most preferably of at least 70% (e.g., measured monolithically).

In the coated article of any of the preceding ten paragraphs, the first crystalline or substantially crystalline layer comprising zinc oxide doped with Sn may be located between and directly contacting the glass substrate and the first IR reflecting layer comprising silver.

In the coated article of any of the preceding eleven paragraphs, the coating may further comprise a first amorphous or substantially amorphous layer comprising zinc stannate located on the glass substrate over at least the first IR reflecting layer comprising silver. The first amorphous or substantially amorphous layer comprising zinc stannate may have a metal content of from about 40-60% Zn and from about 40-60% Sn (wt. %).

In the coated article of any of the preceding twelve paragraphs, the coating may further comprise a contact layer located over and directly contacting the first IR reflecting layer comprising silver. The contact layer may comprise for instance one or more of Ni, Cr, Ni and/or Cr, NiCr, Ti, NiCrMo, and/or oxides and/or nitrides thereof.

In the coated article of any of the preceding thirteen paragraphs, the coating may further comprise: a second IR reflecting layer comprising silver located on the glass substrate over at least the first IR reflecting layer comprising silver, a second crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), located under and directly contacting the second IR reflecting layer comprising silver. Optionally, no silicon nitride based layer is located between the glass substrate and the second IR reflecting layer comprising silver. The coating may also further comprise an amorphous or substantially amorphous layer comprising zinc stannate located on the glass substrate over at least the second IR reflecting layer comprising silver, where the amorphous or substantially amorphous layer comprising zinc stannate may have a metal content of from about 40-60% Zn and from about 40-60% Sn (wt. %). The coating may further comprise a layer comprising silicon nitride located over at least the amorphous or substantially amorphous layer comprising zinc stannate. The coating may further comprise a contact layer (e.g., see example contact layer materials above) located over and directly contacting the second IR reflecting layer comprising silver.

In the coated article of any of the preceding fourteen paragraphs, the coated article may be thermally tempered.

In the coated article of any of the preceding fifteen paragraphs, the coated article may be configured to have, measured monolithically, each of: (i) a transmissive ΔE* value of no greater than 3.5 due to a reference heat treatment for 16 minutes at a temperature of about 650 degrees C., and (ii) a glass side reflective ΔE* value of no greater than 1.8 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding sixteen paragraphs, the coated article may further comprise a layer comprising zirconium oxide located under and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn.

In the coated article of any of the preceding seventeen paragraphs, the coated article may comprise a layer comprising an oxide and/or nitride of silicon and zirconium located under and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn.

In the coated article of any of the preceding eighteen paragraphs, the coated article may comprises a layer comprising an oxide of silicon and zirconium located under and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn. The coated article may further comprise a metallic or substantially metallic absorber layer (e.g., NiCr, NiCrN_(x), NbCr, or NbCrN_(x)) located between the glass substrate and the layer comprising an oxide of silicon and zirconium. The absorber layer may be sandwiched between and contacting first and second layers comprising silicon nitride.

In the coated article of any of the preceding nineteen paragraphs, the coated article may comprise a layer comprising an oxide of silicon and zirconium located between at least the glass substrate and the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn.

In certain example embodiments, there is provided a coated article including a coating on a glass substrate, wherein the coating comprises: a layer comprising zinc oxide doped with from about 1-30% Sn (more preferably from about 5-15%) (wt. %), provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the first layer comprising zinc oxide doped with from about 1-30% Sn; at least one dielectric layer on the glass substrate over at least the first IR reflecting layer comprising silver and the first crystalline or substantially crystalline layer comprising zinc oxide; and wherein no silicon nitride based layer is located directly under and contacting the layer comprising zinc oxide doped with from about 1-30% Sn; and wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.

In the coated article of any of the preceding twenty one paragraphs, the coated article may further comprise a dielectric layer (e.g., see layer 2 in FIGS. 1(b)-(d)) located under and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn. The dielectric layer may comprise one or more of ZrO₂, SiO₂ which may optionally be doped with from 1-10% Al, and/or an oxide of silicon and zirconium. The dielectric layer may be in direct contact with the glass substrate. The dielectric layer may have a physical thickness of from about 40-400 Å, more preferably from about 50-300 Å, and most preferably from about 50-200 Å. The dielectric layer preferably contains little or no nitrogen. For example, the dielectric layer may comprise from 0-20% nitrogen, more preferably from 0-10% nitrogen, and most preferably from 0-5% nitrogen (atomic %).

In the coated article of any of the preceding twenty two paragraphs, the coating may further comprise a second IR reflecting layer comprising silver located on the glass substrate over at least the first IR reflecting layer comprising silver; a second layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), located under and directly contacting the second IR reflecting layer comprising silver; and a layer comprising zinc stannate located between the first IR reflecting layer and the second layer comprising zinc oxide doped with from about 1-30% Sn. There may be provided a layer comprising an oxide of silicon and zirconium located between at least the glass substrate and the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn. The coated article may further include a dielectric layer comprising zirconium oxide (e.g., ZrO₂), and/or an oxide of silicon and zirconium, located between the layer comprising zinc stannate 11 and the second layer 13 comprising zinc oxide doped with from about 1-30% Sn.

Once given the above disclosure many other features, modifications and improvements will become apparent to the skilled artisan. Such other features, modifications and improvements are therefore considered to be a part of this invention, the scope of which is to be determined by the following claims: 

What is claimed is:
 1. A coated article including a coating on a glass substrate, wherein the coating comprises: a first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn; a layer comprising an oxide of silicon and zirconium located under and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn, so that no silicon nitride based layer is located directly under and contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn; and wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.
 2. The coated article of claim 1, wherein the first crystalline or substantially crystalline layer comprising zinc oxide is doped with from about 1-20% Sn (wt. %).
 3. The coated article of claim 1, wherein the first crystalline or substantially crystalline layer comprising zinc oxide is doped with from about 5-15% Sn (wt. %).
 4. The coated article of claim 1, wherein the first crystalline or substantially crystalline layer comprising zinc oxide is doped with about 10% Sn (wt. %).
 5. The coated article of claim 1, wherein the first crystalline or substantially crystalline layer comprising zinc oxide doped with Sn is crystalline or substantially crystalline as sputter-deposited.
 6. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, at least two of: (i) a transmissive ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.
 7. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, all of: (i) a transmissive ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.
 8. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, at least two of: (i) a transmissive ΔE* value of no greater than 2.5 due to a reference heat treatment for 12 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C.
 9. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, all of: (i) a transmissive ΔE* value of no greater than 2.5 due to a reference heat treatment for 12 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 12 minutes at a temperature of about 650 degrees C.
 10. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 2.3 due to a reference heat treatment for 16 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 1.0 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 2.0 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C.
 11. The coated article of claim 1, wherein said coating has a sheet resistance (R_(s)) of no greater than 20 ohms/square.
 12. The coated article of claim 1, wherein said coating has a sheet resistance (R_(s)) of no greater than 10 ohms/square.
 13. The coated article of claim 1, wherein said coating has a sheet resistance (R_(s)) of no greater than 2.2 ohms/square.
 14. The coated article of claim 1, wherein said coated article, measured monolithically, has a visible transmission of at least 50%.
 15. The coated article of claim 1, wherein said coated article, measured monolithically, has a visible transmission of at least 68%.
 16. The coated article of claim 1, wherein the layer comprising an oxide of silicon and zirconium is located between and directly contacting the first crystalline or substantially crystalline layer comprising zinc oxide doped with Sn and the glass substrate.
 17. The coated article of claim 1, wherein the coating as deposited further comprises a first amorphous or substantially amorphous layer comprising zinc stannate located on the glass substrate over at least the first IR reflecting layer comprising silver.
 18. The coated article of claim 17, wherein the first amorphous or substantially amorphous layer comprising zinc stannate has a metal content of from about 40-60% Zn and from about 40-60% Sn (wt. %).
 19. The coated article of claim 1, wherein the coating further comprises a contact layer located over and directly contacting the first IR reflecting layer comprising silver.
 20. The coated article of claim 19, wherein the contact layer comprises Ni and Cr.
 21. The coated article of claim 1, wherein the coating further comprises: a second IR reflecting layer comprising silver located on the glass substrate over at least the first IR reflecting layer comprising silver, a second crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), located under and directly contacting the second IR reflecting layer comprising silver; and wherein no silicon nitride based layer is located between the glass substrate and the second IR reflecting layer comprising silver.
 22. The coated article of claim 21, wherein the coating further comprises an amorphous or substantially amorphous layer, as deposited, comprising zinc stannate located on the glass substrate over at least the second IR reflecting layer comprising silver.
 23. The coated article of claim 22, wherein the amorphous or substantially amorphous layer comprising zinc stannate, which is amorphous or substantially amorphous as deposited, has a metal content of from about 40-60% Zn and from about 40-60% Sn (wt. %).
 24. The coated article of claim 22, wherein the coating further comprises a layer comprising silicon nitride located over at least the amorphous or substantially amorphous layer comprising zinc stannate.
 25. The coated article of claim 22, wherein the coating further comprises a contact layer comprising Ni and/or Cr located over and directly contacting the second IR reflecting layer comprising silver.
 26. The coated article of claim 1, wherein the glass substrate is thermally tempered.
 27. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, each of: (i) a transmissive ΔE* value of no greater than 3.5 due to a reference heat treatment for 16 minutes at a temperature of about 650 degrees C., and (ii) a glass side reflective ΔE* value of no greater than 1.8 due to the reference heat treatment for 16 minutes at a temperature of about 650 degrees C.
 28. The coated article of claim 1, wherein the layer comprising an oxide of silicon and zirconium further comprises nitrogen.
 29. The coated article of claim 1, wherein the coated article further comprises a metallic or substantially metallic absorber layer located between the glass substrate and the layer comprising an oxide of silicon and zirconium.
 30. The coated article of claim 29, wherein the absorber layer is sandwiched between and contacting first and second layers comprising silicon nitride.
 31. The coated article of claim 30, wherein the absorber layer comprises Ni and Cr.
 32. The coated article of claim 1, wherein the coating further comprises: a second IR reflecting layer comprising silver located on the glass substrate over at least the first IR reflecting layer comprising silver; a second layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), located under and directly contacting the second IR reflecting layer comprising silver; and a layer comprising zinc stannate located between the first IR reflecting layer and the second layer comprising zinc oxide doped with from about 1-30% Sn.
 33. The coated article of claim 32, wherein the coated article further comprises a layer comprising zirconium oxide, and/or another layer comprising an oxide of silicon and zirconium, located between the layer comprising zinc stannate and the second layer comprising zinc oxide doped with from about 1-30% Sn.
 34. The coated article of claim 1, wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C. on a reference glass substrate about 3 mm thick, (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C. on a reference glass substrate about 3 mm thick, and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C. on a reference glass substrate about 3 mm thick.
 35. A coated article including a coating on a glass substrate, wherein the coating comprises: a crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn (wt. %), provided on the glass substrate; an infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the layer comprising zinc oxide doped with from about 1-30% Sn; at least one dielectric layer on the glass substrate over at least the IR reflecting layer comprising silver and the crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn; and a layer comprising an oxide of silicon and zirconium located under and directly contacting the crystalline or substantially crystalline layer comprising zinc oxide doped with from about 1-30% Sn, so that no silicon nitride based layer is located directly under and contacting the layer comprising zinc oxide doped with from about 1-30% Sn; and wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.
 36. The coated article of claim 35, wherein the layer comprising zinc oxide is doped with from about 5-15% Sn (wt. %).
 37. The coated article of claim 35, wherein the layer comprising zinc oxide is doped with about 10% Sn (wt. %).
 38. The coated article of claim 35, wherein the layer comprising an oxide of silicon and zirconium is in direct contact with the glass substrate.
 39. The coated article of claim 35, wherein the layer comprising an oxide of silicon and zirconium has a physical thickness of from about 40-400 Å.
 40. The coated article of claim 35, wherein the layer comprising an oxide of silicon and zirconium has a physical thickness of from about 50-300 Å.
 41. The coated article of claim 35, wherein the layer comprising an oxide of silicon and zirconium comprises from 0-10% nitrogen (atomic %).
 42. The coated article of claim 35 wherein the layer comprising an oxide of silicon and zirconium comprises from 0-5% nitrogen (atomic %).
 43. A coated article including a coating on a glass substrate, wherein the coating comprises: a crystalline or substantially crystalline layer comprising zinc oxide doped with at least from 1-30% Sn (wt. %) provided on the glass substrate; a first infrared (IR) reflecting layer comprising silver located on the glass substrate and directly over and contacting the layer comprising zinc oxide doped with at least from 1-30% Sn (wt. %); at least one dielectric layer on the glass substrate over at least the first IR reflecting layer comprising silver and the layer comprising zinc oxide doped with at least from 1-30% Sn (wt. %); wherein no silicon nitride based layer is located directly under and contacting the layer comprising zinc oxide doped with at least from 1-30% Sn (wt. %); a second IR reflecting layer comprising silver located on the glass substrate over at least the first IR reflecting layer and the at least one dielectric layer; a dielectric layer comprising an oxide of silicon and zirconium located on the glass substrate between at least the glass substrate and the layer comprising zinc oxide doped with at least from 1-30% Sn (wt. %), wherein the dielectric layer comprising an oxide of silicon and zirconium directly contacts the layer comprising zinc oxide doped with at least from 1-30% Sn; and wherein the coated article is configured to have, measured monolithically, at least one of: (i) a transmissive ΔE* value of no greater than 3.0 due to a reference heat treatment for 8 minutes at a temperature of about 650 degrees C., (ii) a glass side reflective ΔE* value of no greater than 3.0 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C., and (iii) a film side reflective ΔE* value of no greater than 3.5 due to the reference heat treatment for 8 minutes at a temperature of about 650 degrees C.
 44. The coated article of claim 43, wherein the layer comprising zinc oxide is doped with about 1-20% Sn (wt. %).
 45. The coated article of claim 43, wherein the dielectric layer comprising an oxide of silicon and zirconium is in direct contact with the glass substrate.
 46. The coated article of claim 45, wherein the dielectric layer comprising an oxide of silicon and zirconium has a physical thickness of from about 40-400 Å.
 47. The coated article of claim 43, wherein the dielectric layer comprising an oxide of silicon and zirconium comprises from 0-10% nitrogen (atomic %).
 48. The coated article of claim 43, wherein the coating further comprises: another layer comprising zinc oxide doped with at least one metal, located under and directly contacting the second IR reflecting layer comprising silver; and a layer comprising zinc stannate located between the first IR reflecting layer and the another layer comprising zinc oxide doped with at least one metal. 